Delayed Visits Associated with Increases in TSH Levels Among Patients Using Levothyroxine

Kosuke Inoue, MD, PhD

A recent study from the Ito Hospital in Japan is providing endocrinologists and other clinicians with insight into the effects of delaying visits on thyroid-stimulating hormone (TSH) among patients using levothyroxine during the COVID-19 pandemic.

An analysis of data from more than 25,000 patients who made a follow-up visit during the pandemic in Japan, results of the study indicate delayed visits were associated with an increased risk of elevated TSH levels during the pandemic, with this risk becoming most apparent among those with visits delayed 30 days or more.

“Our study showed that there was a group of patients being treated with levothyroxine who are likely to delay their follow-up visits during the COVID-19 pandemic, and patients who made a delayed follow-up visit showed less well-controlled thyroid hormone levels at their follow-up visits than those who made a follow-up visit as scheduled,” wrote investigators. “Our findings highlight the importance of careful monitoring of patients being treated with levothyroxine during the pandemic.”

As the COVID-19 pandemic has continued longer than many could have anticipated, researchers and clinicians have begun to explore the indirect effects of the pandemic on disease management. Led by Kosuke Inoue, MD, PhD, of Ito Hospital and the UCLA Fielding School of Public Health, the current study was performed with the intent of evaluating the impact of delayed visits during the pandemic on serum thyrotropin levels among those being treated with levothyroxine. To do so, investigators designed their study as an analysis of patients aged 20 years and older treated with levothyroxine at Ito Hospital with a follow-up visit from April-August 2020.

A cohort of 25,361 patients was identified for inclusion. Of these, 9063 attended a follow-up visit as scheduled, 10,909 had a follow-up visit delayed less than 30 days, and 5389 had a follow-up visit delayed 30 days or more. This cohort had a mean age of 52.8 years and 88% were female.

Compared to those who did not have a delayed visit during the pandemic, those who did were more likely to be older and have a higher dose or longer duration of levothyroxine prescription. Investigators noted those who attended telemedicine consultations were not included as thyroid hormone levels were not measured during virtual care.

Upon analysis, results indicated changes in TSH were greater among those with delayed visits (<30 days, -0.52 [95% CI, -0.66 to -0.38]; and ≥30 days, -0.15 [95% CI, -0.36 to 0.06]) than those who attended a scheduled follow-up visit (-0.88 [95% CI, -1.04 to -0.73]). Adjusted analysis indicates those with delayed visits were at a greater risk of elevated TSH levels, with this increase in risk most apparent among those with visits delayed 30 days or more (delayed <30 days, aRR, 1.13 [95% CI, 1.05 to 1.21]; delayed ≥30 days, aRR, 1.72 [95% CI, 1.60 to 1.85]) (delayed <30 days, aRR, 1.17 [95% CI, 1.06 to 1.29]; delayed ≥30 days, aRR, 2.38 [95% CI, 2.16 to 2.62]).

Further analysis suggested stronger associations existed between delayed visits and elevated TSH levels among patients aged 50 years and younger compared to those older than 50 years. Investigators pointed out there were no differences observed in magnitude of association based on patient sex and underlying conditions.

“These findings should raise a concern about the potentially harmful effect of the pandemic on thyroid function control among patients being treated with levothyroxine,” noted investigators.

This study, “Delayed follow-up visits and Thyroid-Stimulating Hormone among patients with levothyroxine during the COVID-19 pandemic,” was published in the Journal of the Endocrine Society.